Formation enthalpies of rare earth titanate pyrochlores

K. B. Helean; S. V. Ushakov; C. E. Brown; A. Navrotsky; J. Lian; R. C. Ewing; J. M. Farmer; L. A. Boatner

doi:10.1016/j.jssc.2004.01.009

Formation enthalpies of rare earth titanate pyrochlores

K. B. Helean, S. V. Ushakov, C. E. Brown, A. Navrotsky, J. Lian, R. C. Ewing, J. M. Farmer, L. A. Boatner

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146 Scopus citations

Abstract

High-temperature oxide melt solution calorimetry and Rietveld refinements of powder X-ray diffraction data were used to investigate the structure (Fd3m; Z=8) and energetics of a series of RE₂Ti₂O₇ (RE=Sm-Lu) compounds with the pyrochlore structure as well as La ₂Ti₂O₇ with a layered perovskite-type structure. All of the RE-titanates were found to be stable in enthalpy with respect to their oxides. In the pyrochlore series, Lu₂Ti ₂O₇ was least stable in enthalpy (ΔHf-ox at 298K=-56.0±4.0kJ/mol); the most stable materials were Gd-, Eu-, and Sm₂Ti₂O₇ with ΔHf-ox at 298K=-113.4±2.7, -106.1±4.2, -115.4±4.2kJ/mol, respectively. In general, as the radius ratio of the A- to B-site cations, R_A/R_B, decreases, the pyrochlore structure becomes less stable. The trend of ionic radius of the RE³⁺ cation vs. ΔHf-ox at 298K is non-linear and approximately parallels the increasing "resistance" to ion-beam-induced amorphization as R_A/R _B decreases.

Original language	English (US)
Pages (from-to)	1858-1866
Number of pages	9
Journal	Journal of Solid State Chemistry
Volume	177
Issue number	6
DOIs	https://doi.org/10.1016/j.jssc.2004.01.009
State	Published - Jun 2004
Externally published	Yes

Keywords

Enthalpy
Nuclear waste
Pyrochlore
Thermodynamics

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Ceramics and Composites
Condensed Matter Physics
Physical and Theoretical Chemistry
Inorganic Chemistry
Materials Chemistry

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10.1016/j.jssc.2004.01.009

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@article{cbefc5bd12dd48129e0af8449fa632e4,

title = "Formation enthalpies of rare earth titanate pyrochlores",

abstract = "High-temperature oxide melt solution calorimetry and Rietveld refinements of powder X-ray diffraction data were used to investigate the structure (Fd3m; Z=8) and energetics of a series of RE2Ti2O7 (RE=Sm-Lu) compounds with the pyrochlore structure as well as La 2Ti2O7 with a layered perovskite-type structure. All of the RE-titanates were found to be stable in enthalpy with respect to their oxides. In the pyrochlore series, Lu2Ti 2O7 was least stable in enthalpy (ΔHf-ox at 298K=-56.0±4.0kJ/mol); the most stable materials were Gd-, Eu-, and Sm2Ti2O7 with ΔHf-ox at 298K=-113.4±2.7, -106.1±4.2, -115.4±4.2kJ/mol, respectively. In general, as the radius ratio of the A- to B-site cations, RA/RB, decreases, the pyrochlore structure becomes less stable. The trend of ionic radius of the RE3+ cation vs. ΔHf-ox at 298K is non-linear and approximately parallels the increasing {"}resistance{"} to ion-beam-induced amorphization as RA/R B decreases.",

keywords = "Enthalpy, Nuclear waste, Pyrochlore, Thermodynamics",

author = "Helean, {K. B.} and Ushakov, {S. V.} and Brown, {C. E.} and A. Navrotsky and J. Lian and Ewing, {R. C.} and Farmer, {J. M.} and Boatner, {L. A.}",

note = "Funding Information: Financial support was provided by the University of California at Davis and by the Office of Basic Energy Sciences, DOE grant DE-FG02-97ER45656 (RCE). Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the US Department of Energy under contract DE-AC05-00OR22725. ",

year = "2004",

month = jun,

doi = "10.1016/j.jssc.2004.01.009",

language = "English (US)",

volume = "177",

pages = "1858--1866",

journal = "Journal of Solid State Chemistry",

issn = "0022-4596",

publisher = "Academic Press Inc.",

number = "6",

}

TY - JOUR

T1 - Formation enthalpies of rare earth titanate pyrochlores

AU - Helean, K. B.

AU - Ushakov, S. V.

AU - Brown, C. E.

AU - Navrotsky, A.

AU - Lian, J.

AU - Ewing, R. C.

AU - Farmer, J. M.

AU - Boatner, L. A.

N1 - Funding Information: Financial support was provided by the University of California at Davis and by the Office of Basic Energy Sciences, DOE grant DE-FG02-97ER45656 (RCE). Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the US Department of Energy under contract DE-AC05-00OR22725.

PY - 2004/6

Y1 - 2004/6

N2 - High-temperature oxide melt solution calorimetry and Rietveld refinements of powder X-ray diffraction data were used to investigate the structure (Fd3m; Z=8) and energetics of a series of RE2Ti2O7 (RE=Sm-Lu) compounds with the pyrochlore structure as well as La 2Ti2O7 with a layered perovskite-type structure. All of the RE-titanates were found to be stable in enthalpy with respect to their oxides. In the pyrochlore series, Lu2Ti 2O7 was least stable in enthalpy (ΔHf-ox at 298K=-56.0±4.0kJ/mol); the most stable materials were Gd-, Eu-, and Sm2Ti2O7 with ΔHf-ox at 298K=-113.4±2.7, -106.1±4.2, -115.4±4.2kJ/mol, respectively. In general, as the radius ratio of the A- to B-site cations, RA/RB, decreases, the pyrochlore structure becomes less stable. The trend of ionic radius of the RE3+ cation vs. ΔHf-ox at 298K is non-linear and approximately parallels the increasing "resistance" to ion-beam-induced amorphization as RA/R B decreases.

AB - High-temperature oxide melt solution calorimetry and Rietveld refinements of powder X-ray diffraction data were used to investigate the structure (Fd3m; Z=8) and energetics of a series of RE2Ti2O7 (RE=Sm-Lu) compounds with the pyrochlore structure as well as La 2Ti2O7 with a layered perovskite-type structure. All of the RE-titanates were found to be stable in enthalpy with respect to their oxides. In the pyrochlore series, Lu2Ti 2O7 was least stable in enthalpy (ΔHf-ox at 298K=-56.0±4.0kJ/mol); the most stable materials were Gd-, Eu-, and Sm2Ti2O7 with ΔHf-ox at 298K=-113.4±2.7, -106.1±4.2, -115.4±4.2kJ/mol, respectively. In general, as the radius ratio of the A- to B-site cations, RA/RB, decreases, the pyrochlore structure becomes less stable. The trend of ionic radius of the RE3+ cation vs. ΔHf-ox at 298K is non-linear and approximately parallels the increasing "resistance" to ion-beam-induced amorphization as RA/R B decreases.

KW - Enthalpy

KW - Nuclear waste

KW - Pyrochlore

KW - Thermodynamics

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U2 - 10.1016/j.jssc.2004.01.009

DO - 10.1016/j.jssc.2004.01.009

M3 - Article

AN - SCOPUS:3242707952

SN - 0022-4596

VL - 177

SP - 1858

EP - 1866

JO - Journal of Solid State Chemistry

JF - Journal of Solid State Chemistry

IS - 6

ER -

Formation enthalpies of rare earth titanate pyrochlores

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Keywords

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